US5339157A - Rapidly tunable integrated optical filter - Google Patents

Rapidly tunable integrated optical filter Download PDF

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Publication number
US5339157A
US5339157A US08019961 US1996193A US5339157A US 5339157 A US5339157 A US 5339157A US 08019961 US08019961 US 08019961 US 1996193 A US1996193 A US 1996193A US 5339157 A US5339157 A US 5339157A
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plurality
waveguides
connected
input
optical
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US08019961
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Bernard Glance
Robert W. Wilson
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Nokia Bell Labs
AT&T Corp
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Nokia Bell Labs
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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B6/00Light guides
    • G02B6/10Light guides of the optical waveguide type
    • G02B6/12Light guides of the optical waveguide type of the integrated circuit kind
    • G02B6/12007Light guides of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
    • G02B6/12009Light guides of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides
    • G02B6/12019Light guides of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides characterised by the optical interconnection to or from the AWG devices, e.g. integration or coupling with lasers or photodiodes
    • G02B6/12021Comprising cascaded AWG devices; AWG multipass configuration; Plural AWG devices integrated on a single chip
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0003Details

Abstract

A monolithically integrated optical filter which is rapidly tunable over a wide optical frequency range comprises an input frequency router connected to an output frequency router by means of controllably transmissive waveguides. A control circuit applies electrical energy to predetermined controllably transmissive waveguides to tune the optical filter to a desired one or more of a plurality of multiplexed input optical frequencies. This filter is economical to construct and is useful in high capacity, high speed optical communications networks.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to application Ser. No. 08/019,957 (still pending) of Bernard Glance and Robert Wilson, entitled "Rapidly Tunable Wideband Integrated Optical Filter," filed in the Patent and Trademark Office on the same day this application is being filed.

This application is related to application Ser. No. 08/019,952 (still pending) of Corrado Dragone and Ivan Kaminow, entitled "Rapidly Tunable Integrated Laser," filed in the Patent and Trademark Office on the same day this application is being filed.

This application is related to application Ser. No. 08/019,951 (still pending) of Bernard Glance and Robert Wilson, entitled "Rapidly Tunable Wideband Integrated Laser," filed in the Patent and Trademark Office on the same day this application is being filed.

TECHNICAL FIELD

This invention relates to optical communications systems. More particularly, this invention relates to integrated optical filters used in optical communications systems.

BACKGROUND

The capacity and speed of communications systems may be increased by transmitting information in optical form over networks composed of optically transmissive nodes, fibers, waveguides, and the like. High capacity optical communications systems require that many optical signals be frequency division multiplexed in the components of an optical network. Receivers must be configured such that a desired optical frequency may be retrieved from a group of many multiplexed optical frequencies. This necessitates the provision of suitable optical filters which separate desired optical frequencies from a frequency division multiplexed plurality of optical frequencies. Until now, there has been no convenient approach to filtering unwanted optical frequencies from desired optical frequencies. The performance of prior tunable optical filters, based on electro-michanical, electro-optic, acousto-optic, and magneto-optic effects, have been limited in terms of tuning speed, frequency selectivity, or tuning range. All of these prior devices also have been expensive to implement.

SUMMARY

In accordance with this invention, a rapidly tunable optical filter has been developed. The optical filter in accordance with this invention may be based upon photonic integrated circuitry which can provide a great deal of frequency selectivity and a wide tuning range which can be realized at a cost lower than that associated with implementing prior optical filters.

In one example of the invention, Applicants have surprisingly realized that integrated optical multiplexers and demultiplexers disclosed, for example, in U.S. Pat. No. 5,002,350 and U.S. Pat. No. 5,136,671 may be used to areate a monolithic fast optical filter having a wide tuning range. In specific terms, this example of the invention comprises two identical 1×N frequency routing devices with their frequency selective ports interconnected. Each path connecting the two devices contains an integrated optical amplifier acting as a gate. An input signal containing several different frequency channels is divided among output ports of the first frequency routing device and directed to respective inputs of the second frequency routing device. The second frequency routing device may output any selected frequency from the multiplexed combination of frequencies. Any of these channels may be selected by opening a respective gate by activating a respective optical amplifier between the first and second frequency routing devices. The other channels remain highly attenuated because of the inactivation of their respective optical amplifiers. Thus, only the selected channel exits the second frequency routing device. Broadband amplifier noise is filtered since only frequency noise components corresponding to the selected frequency path exit the second frequency routing device. The remaining amplifier noise is dissipated into the other N-1 unused outputs of the second frequency routing device.

This is only an example of the invention. The full scope of the invention entitled to an exclusionary right is set forth in the claims at the end of this application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example of a tunable optical filter in accordance with this invention.

FIG. 2 is a diagram illustrating the details of the frequency routing devices shown in FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows an example of an optical filter which is rapidly tunable over a wide frequency range. It is composed of frequency routing devices, waveguides, and optically active sections. These structures may be monolithically integrated on a semiconductive wafer. They may be created by means of known photolithographic techniques.

FIG. 1 illustrates a wafer 10 made of a semiconductive material such as an indium phosphide based material such as InGaAsP. A first input frequency routing device 12 is defined on the wafer 10. The frequency routing device 12 may receive N multiplexed input optical frequencies F1, F2, . . . , FN on a single input waveguide 14 defined on the wafer 10. The first frequency routing device 12 demultiplexes the input optical frequencies and directs each one of those frequencies into a separate output waveguide connected to the output of the frequency routing device 12. Specifically, frequency F1 is directed to the output waveguide 161, frequency F2 is directed to the output waveguide 162, and so on up to frequency FN which is directed to output waveguide 16N. Each of the output waveguides 161, 162, . . . , 16N is directed to the input of a doped section of waveguide with controllable optical transmissivity. The doping may be such that a suitable semiconductor Junction is created. These doped sections are optically active in that application of electrical energy to those sections will cause them to become transmissive to the flow of optical energy and will even provide some degree of gain to optical signals flowing through them. These doped sections of waveguide are substantially opaque to the transmission of light when there is no applied electrical stimulation. The specially doped sections thus may be considered to be gates or optical amplifiers depending upon whether or not they are excited with electrical energy. The details of creating such sections in a wafer such as the indium phosphide wafer 10 shown in FIG. 1 are generally known, are not a part of this invention, and thus are not described here.

Specifically in FIG. 1, an output waveguide 161 is directed to the input of an optically active section 181, an output waveguide 162 is directed to the input of an optically active section 182, and so on up to an output waveguide 16N directed to the input of an optically active section 18N.

The outputs of the active sections 181, 182, . . . , 18N are connected to respective input waveguides 201, 202, . . . , 20N of an output frequency routing device 22. The frequency routing device 22 will multiplex single frequencies appearing on the N input waveguides onto a single output waveguide 24, if all of the active sections between the input router 12 and the output router 22 are activated with electrical energy. If only one of the active sections is stimulated with electrical energy, then only the frequency flowing in that activated section will appear on the output waveguide 24. The device shown in FIG. 1 thus acts as an optical filter for the multiplexed input frequencies appearing on waveguide 14 when appropriate active sections are stimulated. Accordingly, a digital gate control circuit 26 is provided for the structure of FIG. 1 which selectively applies electrical energy to predetermined ones of the sections between the frequency routers so that unwanted frequencies in the input stream to the device of FIG. 1 may be suppressed and one or more desired frequencies may be obtained from the output of the device of FIG. 1.

FIG. 2 shows the pertinent details of the routing devices 12 and 22 shown in FIG. 1. Both of those devices may have identical configurations. Each frequency routing device contains a plurality of input waveguides 26 connected to a free space region 28. A plurality of output waveguides 30 extends from the free space region 28 and is connected to an optical grating 32. The optical grating 32 comprises a plurality of unequal length waveguides which provides a predetermined amount of path length difference to a corresponding plurality of input waveguides 34 connected to another free space region 36. The free space region 36 is connected to a plurality of output waveguides 38. These frequency routing devices operate as multiplexers and demultiplexers of optical frequencies. The details of their construction and operation are more fully described in the U.S. patents referred to above, the entire contents of which are hereby incorporated by reference into this application. In the case of the frequency routing device 12, one of the input waveguides 26 is used as the input waveguide 14 of the device shown in FIG. 1 and the plurality of output waveguides 38 are used as the output waveguides 161, 162, . . . , 16N. In the case of the frequency routing device 22, the plurality of input waveguides 26 are the input waveguides 201, 202, . . . , 20N shown in FIG. 1 and one of the output waveguides 38 is the output waveguide 24 shown in FIG. 1.

The device of FIG. 1 may be tuned to a large number of different optical frequencies used in high speed, high capacity optical communications networks. For example, frequency routing devices with N up to 32 or more may be conveniently fabricated on a single semiconductive wafer. This results in an optical filter which can be tuned to any of up to 32 or more optical frequencies. The doped sections between the frequency router in FIG. 1 may be switched on or off at up to nanosecond speeds thereby resulting in rapid tuning of the FIG. 1 filter to the desired frequencies. Devices such as the filter in FIG. 1 are attractive for large size optical network applications based on frequency division multiplexing.

Claims (7)

We claim:
1. A tunable integrated optical filter, comprising:
an input frequency routing device for receiving a plurality of multiplexed optical frequencies; and
an output frequency routing device responsive to the input frequency routing device for producing an optical output representing a selected one or more of the multiplexed optical frequencies.
2. The optical filter of claim 1, further comprising:
a plurality of waveguides connecting a plurality of outputs from the input frequency routing device to a plurality of inputs of the output frequency routing device;
each of the plurality of waveguides comprising a controllably transmissive section.
3. The optical filter of claim 2, further comprising:
a control circuit for selectively applying electrical energy to a predetermined one or more of the controllably transmissive sections for tuning the optical filter to a predetermined one or more of the plurality of multiplexed optical frequencies received by the input frequency routing device.
4. The optical filter of claim 1, in which the input frequency routing device comprises:
at least one input waveguide;
a first free space region connected to the at least one input waveguide;
a plurality of output waveguides connected to the first free space region;
an optical grating connected to the plurality of output waveguides comprising a plurality of unequal length waveguides;
a plurality of input waveguides connected to the optical grating;
a second free space region connected to the plurality of input waveguides connected to the optical grating; and
a plurality of output waveguides connected to the second free space region.
5. The optical filter of claim 1, in which the output frequency routing device comprises:
a plurality of input waveguides;
a first free space region connected to the plurality of input waveguides;
a plurality of output waveguides connected to the first free space region;
an optical grating connected to the plurality of output waveguides comprising a plurality of unequal length waveguides;
a plurality of input waveguides connected to the optical grating;
a second free space region connected to the plurality of input waveguides connected to the optical grating; and
at least one output waveguide connected to the second free space region.
6. The optical filter of claim 4, in which the output frequency routing device comprises:
a plurality of input waveguides;
a first free space region connected to the plurality of input waveguides;
a plurality of output waveguides connected to the first free space region;
an optical grating connected to the plurality of output waveguides comprising a plurality of unequal length waveguides;
a plurality of input waveguides connected to the optical grating;
a second free space region connected to the plurality of input waveguides connected to the optical grating; and
at least one output waveguide connected to the second free space region.
7. The optical filter of claim 6, in which each of the plurality of output waveguides of the input frequency routing device are connected to a respective one of the plurality of input waveguides of the output frequency routing device by means of one of the controllably transmissive sections.
US08019961 1993-02-19 1993-02-19 Rapidly tunable integrated optical filter Expired - Lifetime US5339157A (en)

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US08019961 US5339157A (en) 1993-02-19 1993-02-19 Rapidly tunable integrated optical filter
EP19940300940 EP0612165A1 (en) 1993-02-19 1994-02-09 Rapidly tunable integrated optical filter
JP4065994A JPH06250133A (en) 1993-02-19 1994-02-16 Optical filter device

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Cited By (35)

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Publication number Priority date Publication date Assignee Title
US5412744A (en) * 1994-05-02 1995-05-02 At&T Corp. Frequency routing device having a wide and substantially flat passband
US5416866A (en) * 1992-08-26 1995-05-16 Telefonaktiebolaget L M Ericsson Optical waveguide/grating device for filtering optical wavelengths
US5461685A (en) * 1993-10-18 1995-10-24 At&T Ipm Corp. Optical passband filter
US5467418A (en) * 1994-09-02 1995-11-14 At&T Ipm Corp. Frequency routing device having a spatially filtered optical grating for providing an increased passband width
US5473719A (en) * 1993-11-15 1995-12-05 At&T Corp. Optical dispersion compensator
US5479544A (en) * 1992-10-03 1995-12-26 Canon Kabushiki Kaisha Optical receiver, optical semiconductor apparatus, and optical communication system utilizing the same
US5488680A (en) * 1994-08-24 1996-01-30 At&T Corp. Frequency routing device having a wide and substantially flat passband
US5493625A (en) * 1993-11-16 1996-02-20 At&T Corp. Fast tunable channel dropping filter
US5504827A (en) * 1993-08-06 1996-04-02 Siemens Aktiengesellschaft Programmable optical filter and optical circuit arrangement
US5509023A (en) * 1994-03-10 1996-04-16 At&T Corp. Laser control arrangement for tuning a laser
US5524014A (en) * 1994-05-23 1996-06-04 At&T Corp. Optical frequency translator
US5542010A (en) * 1993-02-19 1996-07-30 At&T Corp. Rapidly tunable wideband integrated optical filter
US5566014A (en) * 1994-12-28 1996-10-15 At&T Corp. Tunable add/drop optical filter providing arbitrary channel arrangements
US5600742A (en) * 1994-09-30 1997-02-04 Lucent Technologies Inc. Wavelength grating router with output coupler
US5623571A (en) * 1995-08-29 1997-04-22 Lucent Technologies Inc. Polarization compensated waveguide grating router
US5675592A (en) * 1994-05-23 1997-10-07 Lucent Technologies Inc. Rapidly tunable integrated laser
US5680490A (en) * 1995-09-08 1997-10-21 Lucent Technologies Inc. Comb splitting system and method for a multichannel optical fiber communication network
US5706377A (en) * 1996-07-17 1998-01-06 Lucent Technologies Inc. Wavelength routing device having wide and flat passbands
US5740289A (en) * 1996-12-30 1998-04-14 At&T Corp Optical arrangement for amplifying WDM signals
US5745616A (en) * 1996-11-27 1998-04-28 Lucent Technologies Inc. Waveguide grating router and method of making same having relatively small dimensions
US5745618A (en) * 1997-02-04 1998-04-28 Lucent Technologies, Inc. Optical device having low insertion loss
US5751872A (en) * 1995-12-28 1998-05-12 Alcatel Alsthom Compagnie Generale D'electricite Wavelength demultiplexer
US5841919A (en) * 1996-08-02 1998-11-24 Hitachi Cable, Ltd. Optical wavelength multiplexer/demultiplexer
US5845022A (en) * 1997-02-14 1998-12-01 Doerr; Christopher Richard Double-chirped waveguide grating router with angled ports
US5940555A (en) * 1997-02-14 1999-08-17 Hitachi Cable, Ltd. Optical multiplexer/demultiplexer
US5943452A (en) * 1996-08-06 1999-08-24 Nippon Telegraph And Telephone Corporation Arrayed-waveguide grating
DE19815404A1 (en) * 1998-04-06 1999-10-14 Siemens Ag Arrangement for physical separation and / or collection of optical wavelength channels
US6014390A (en) * 1998-01-30 2000-01-11 Lucent Technologies Inc. Tunable transmitter with Mach-Zehnder modulator
US6240118B1 (en) * 1998-11-16 2001-05-29 Lucent Technologies Inc. Multichannel laser transmitter with a single output port
US6272270B1 (en) * 1997-07-11 2001-08-07 Oki Electric Industry Co., Ltd. Optical wave combining/splitting device
US6282344B1 (en) * 1999-12-08 2001-08-28 Agere Systems Optoelectronics Guardian Corp. Intersecting N x M star couplers for routing optical signals
US6498682B2 (en) 1998-12-28 2002-12-24 At&T Corp. Tunable add/drop filter
US6556742B2 (en) * 1998-11-04 2003-04-29 Fujitsu Limited Optical wavelength division multiplexed system using wavelength splitters
US6594049B1 (en) * 1999-10-29 2003-07-15 Lucent Technologies Inc. Optical router
US6766074B1 (en) 2001-08-15 2004-07-20 Corning Incorporated Demultiplexer/multiplexer with a controlled variable path length device

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US5444725A (en) * 1994-09-30 1995-08-22 At&T Ipm Corp. Multifrequency laser
US5701371A (en) * 1994-10-31 1997-12-23 Nippon Telegraph And Telephone Corporation Tunable optical filter
EP0950297B1 (en) 1996-12-23 2002-08-28 Tellabs Denmark A/S A bidirectional router and a method of monodirectional amplification
JP4168480B2 (en) 1998-02-27 2008-10-22 ダイキン工業株式会社 Fluororubber aqueous coating compositions and coated articles
JP2001085800A (en) * 1999-09-09 2001-03-30 Hitachi Ltd Semiconductor optical amplifier module, and, optical communication system
JP4728530B2 (en) * 2001-08-24 2011-07-20 古河電気工業株式会社 Integrated optical device
US7149373B2 (en) * 2004-02-02 2006-12-12 Lucent Technologies Inc. Active/passive monolithically integrated channel filtering polarization splitter

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Cited By (40)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5416866A (en) * 1992-08-26 1995-05-16 Telefonaktiebolaget L M Ericsson Optical waveguide/grating device for filtering optical wavelengths
US5479544A (en) * 1992-10-03 1995-12-26 Canon Kabushiki Kaisha Optical receiver, optical semiconductor apparatus, and optical communication system utilizing the same
US5542010A (en) * 1993-02-19 1996-07-30 At&T Corp. Rapidly tunable wideband integrated optical filter
US5504827A (en) * 1993-08-06 1996-04-02 Siemens Aktiengesellschaft Programmable optical filter and optical circuit arrangement
US5461685A (en) * 1993-10-18 1995-10-24 At&T Ipm Corp. Optical passband filter
US5473719A (en) * 1993-11-15 1995-12-05 At&T Corp. Optical dispersion compensator
US5493625A (en) * 1993-11-16 1996-02-20 At&T Corp. Fast tunable channel dropping filter
US5509023A (en) * 1994-03-10 1996-04-16 At&T Corp. Laser control arrangement for tuning a laser
US5412744A (en) * 1994-05-02 1995-05-02 At&T Corp. Frequency routing device having a wide and substantially flat passband
US5675592A (en) * 1994-05-23 1997-10-07 Lucent Technologies Inc. Rapidly tunable integrated laser
US5524014A (en) * 1994-05-23 1996-06-04 At&T Corp. Optical frequency translator
US5488680A (en) * 1994-08-24 1996-01-30 At&T Corp. Frequency routing device having a wide and substantially flat passband
US5467418A (en) * 1994-09-02 1995-11-14 At&T Ipm Corp. Frequency routing device having a spatially filtered optical grating for providing an increased passband width
US5600742A (en) * 1994-09-30 1997-02-04 Lucent Technologies Inc. Wavelength grating router with output coupler
US5566014A (en) * 1994-12-28 1996-10-15 At&T Corp. Tunable add/drop optical filter providing arbitrary channel arrangements
US5623571A (en) * 1995-08-29 1997-04-22 Lucent Technologies Inc. Polarization compensated waveguide grating router
US5680490A (en) * 1995-09-08 1997-10-21 Lucent Technologies Inc. Comb splitting system and method for a multichannel optical fiber communication network
US5751872A (en) * 1995-12-28 1998-05-12 Alcatel Alsthom Compagnie Generale D'electricite Wavelength demultiplexer
US5706377A (en) * 1996-07-17 1998-01-06 Lucent Technologies Inc. Wavelength routing device having wide and flat passbands
US5841919A (en) * 1996-08-02 1998-11-24 Hitachi Cable, Ltd. Optical wavelength multiplexer/demultiplexer
US5943452A (en) * 1996-08-06 1999-08-24 Nippon Telegraph And Telephone Corporation Arrayed-waveguide grating
US5745616A (en) * 1996-11-27 1998-04-28 Lucent Technologies Inc. Waveguide grating router and method of making same having relatively small dimensions
US5740289A (en) * 1996-12-30 1998-04-14 At&T Corp Optical arrangement for amplifying WDM signals
US5745618A (en) * 1997-02-04 1998-04-28 Lucent Technologies, Inc. Optical device having low insertion loss
US5845022A (en) * 1997-02-14 1998-12-01 Doerr; Christopher Richard Double-chirped waveguide grating router with angled ports
US5940555A (en) * 1997-02-14 1999-08-17 Hitachi Cable, Ltd. Optical multiplexer/demultiplexer
US6272270B1 (en) * 1997-07-11 2001-08-07 Oki Electric Industry Co., Ltd. Optical wave combining/splitting device
US6014390A (en) * 1998-01-30 2000-01-11 Lucent Technologies Inc. Tunable transmitter with Mach-Zehnder modulator
US6591034B1 (en) 1998-04-06 2003-07-08 Infineon Technologies Ag Configuration for spatially separating and/or joining optical wavelength channels
DE19815404A1 (en) * 1998-04-06 1999-10-14 Siemens Ag Arrangement for physical separation and / or collection of optical wavelength channels
US20050259915A1 (en) * 1998-11-04 2005-11-24 Fujitsu Limited Optical wavelength division multiplexed system using wavelength splitters
US6901183B2 (en) 1998-11-04 2005-05-31 Fujitsu Limited Optical wavelength division multiplexed system using wavelength splitters
US20030179989A1 (en) * 1998-11-04 2003-09-25 Fujitsu Limited Optical wavelength division multiplexed system using wavelength splitters
US6556742B2 (en) * 1998-11-04 2003-04-29 Fujitsu Limited Optical wavelength division multiplexed system using wavelength splitters
US7171071B2 (en) 1998-11-04 2007-01-30 Fujitsu Limited Optical wavelength division multiplexed system using wavelength splitters
US6240118B1 (en) * 1998-11-16 2001-05-29 Lucent Technologies Inc. Multichannel laser transmitter with a single output port
US6498682B2 (en) 1998-12-28 2002-12-24 At&T Corp. Tunable add/drop filter
US6594049B1 (en) * 1999-10-29 2003-07-15 Lucent Technologies Inc. Optical router
US6282344B1 (en) * 1999-12-08 2001-08-28 Agere Systems Optoelectronics Guardian Corp. Intersecting N x M star couplers for routing optical signals
US6766074B1 (en) 2001-08-15 2004-07-20 Corning Incorporated Demultiplexer/multiplexer with a controlled variable path length device

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JPH06250133A (en) 1994-09-09 application
EP0612165A1 (en) 1994-08-24 application

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